Methods for the fractionation and analysis of proteins are developed and applied to the purification of specific proteins for the study of their function and structure. Displacement chromatography is being developed for the fractionation of macromolecules and particles of biological interest, employing polyanions differing in number of charges per molecule as displacers. Current efforts are directed toward the fractionation of nonhistone proteins of calf thymus nuclei and marker proteins in human serum. The procedure is particularly advantageous when large amounts of source material must be used to obtain sufficient amounts of a minor component.